Method for hydrophobizing a cellulose substrate by utilizing a fatty acid halide

ABSTRACT

The present invention relates to a method for hydrophobizing a cellulose substrate (1), which comprising a first side and a second side, which faces away from the first side, the method comprising the steps of: —drying the cellulose substrate to a dry content above 80%, preferably above 85%; —providing a fatty acid halide in spray form; —converting said fatty acid halide in spray form into vaporized fatty acid halide; and —guiding said vaporized fatty acid halide to contact the first side of the cellulose substrate, and at least partially penetrate the cellulose substrate.

FIELD OF INVENTION

Method for hydrophobizing a cellulose substrate, which substratecomprises a first side and an opposite second side.

BACKGROUND

There is a need to increase the hydrophobicity of materials based oncellulose in several fields, e.g. in the textile industry and the paper-and paperboard industry.

Paper- and paperboard are usually treated with sizing agents to enhancecertain qualities, above all to increase the resistance to penetrationof water and other liquids into the paper or paperboard. There are twotypes of sizing: internal and surface sizing. In internal sizing,chemicals are added to the pulp at the wet end, e.g. ASA, AKD or rosinsize. Common surface sizing agents include e.g. starch or acrylicco-polymers.

U.S. Pat. No. 4,107,426 discloses a method for imparting water-repellentcharacteristics to a surface of a cellulose substrate. The processcomprising the steps of exposing the surface to a vapour phaseconsisting essentially of aliphatic acid chloride.

A drawback with this method is that mainly the surface of a substratethat becomes hydrophobic and not the interior of the substrate. Thiscauses problem with edge wicking, i.e. penetration of liquid into theedges of a substrate.

In WO2017002005, a method is described where a vaporized fatty acidhalide is arranged to penetrate the cellulose substrate. However, theequipment required to perform the method according to WO2017002005occupies a lot of space and is therefore difficult to implement at anexisting production site.

An object with the present invention is to provide an improved methodfor increasing the hydrophobicity of materials with a cellulosesubstrate that e.g. enhances the water repellency and resistance againstedge wick penetration of a cellulose substrate.

SUMMARY OF THE INVENTION

The inventive method for hydrophobizing a cellulose substrate comprisingthe following steps:

-   -   drying the cellulose substrate to a dry content above 80%,        preferably above 85%;    -   providing a fatty acid halide in spray form;    -   converting said fatty acid halide in spray form into vaporized        fatty acid halide;        and    -   guiding said vaporized fatty acid halide to contact the first        side of the cellulose substrate, and at least partially        penetrate the cellulose substrate.

Treating a cellulose substrate according to the method of the presentinvention leads to an increase of the hydrophobicity of the material,not only at the surface but also at its core, and to enhanced waterresistance thereof, as well as resistance against edge wick penetrationof a cellulose substrate.

Several additional advantages are also achieved thanks to the methodaccording to the invention. For example:

-   -   the device for applying the vaporized fatty acid halide onto the        substrate can be aimed in differently defined directions,    -   the reagent (i.e. fatty acid halide) will have an even        distribution over the surface even if the surface is rough,    -   calibration of dosage enables for avoiding unwanted surplus of        reagent on substrate,    -   the amount of reagent can be easily controlled by adjusting the        pressure or the number of spray units, and    -   the nozzles/units do not require large space which facilitates        installation at an existing on-line production site.

It is to be understood that “spray form” means in the form of aplurality of liquid droplets or particles, and that the fatty acidhalide in spray form may be delivered by means of a precision device fordispersion of freely flowing liquid fatty acid halide into said sprayform. The droplets or particles may be in micro scale with sizes rangingfrom 1-900 μm in diameter.

According to another aspect of the invention, the vaporized fatty acidhalide is guided to contact also the second side of the cellulosesubstrate, and at least partially penetrate the cellulose substrate.This may be accomplished by means of vacuum suction.

The cellulose substrate can be in the form of paper- or paperboard web,paperboard application, textiles made from cellulose fibres, orthree-dimensional cellulose-based products e.g. produced by means ofthermoforming.

The paper- or paperboard web may be a single- or multilayer web.

Conversion of the fatty acid halide spray into vaporized form may beaccomplished by applying thermal energy, i.e. heating the spray dropletsto a point where they enter gaseous state. As an example, heating of thespray can be performed by IR heating. Other heating devices areconceivable, such as e.g. a hot cylinder, microwaves or similar.Vaporizing of fatty acid halide in spray form requires lower energyconsumption compared to vaporizing a freely flowing liquid into gas. Asa beneficial consequence, the equipment for converting the spray intogas can be made space efficient and therefore be fitted at an existingproductions line.

According to another aspect of the invention, said guiding of the fattyacid halide is performed by vacuum sucking at the second side of thecellulose substrate, such that the fatty acid penetrates the cellulosesubstrate in a predetermined direction through the cellulose substrate.Such vacuum suction can be generated by means of a vacuum box, arotating vacuum cylinder or any other suitable vacuum generatingequipment. Thanks to the method according to the invention, the covalentdegree can be more even throughout the thickness of the materialcompared to e.g. conventional roll coating of freely flowing reagentsonto a running substrate.

The covalent degree is the ratio between the grafted fatty acids and thetotal fatty acids in the substrate, where the grafted corresponds to thereagent that has reacted and the total amount is this part together withthe free fatty acids that only has been physically absorbed to thesubstrate.

According to another aspect of the invention, said guiding of thevaporized fatty acid halide is performed by vacuum sucking at the firstside of the cellulose substrate, so that the vaporized fatty acid isguided along the surface of the first side of the cellulose substrate ina predetermined direction in such a way that the fatty acid is broughtinto contact with the cellulose substrate. In one example, “along thesurface” means that the vaporized fatty acid is brought to movesubstantially parallel with the first side of the substrate for acontrolled distance (depending on the substrate).

According to another aspect of the invention, the fatty acid halide ismixed with at least one solvent before it is sprayed and vaporized.Preferably, said solvent is selected from the group comprising: acetone,ethyl acetate and methyl ethyl ketone. It is preferred that the solvent(or mixture of solvents) does not contain any OH-groups, and also thatit is miscible with the fatty acid halide, which will help againstclogging and promote the cleaning of the application system. Theutilization of a solvent also makes it possible to minimize and controlthe amount of applied fatty acid halide in a better way.

The boiling point of the solvent shall preferably not be too high toensure that there will be no residual solvent in the product, preferablyit is below 200 degrees C., more preferably below 150 degrees C., andeven more preferably below 100 degrees C. Acetone has a boiling point at59 degrees C.; ethyl acetate has a boiling point at 77 degrees C. andmethyl ethyl ketone has a boiling point at below 59 degrees C. Additionof a solvent to the fatty acid halide may lead to the advantage thatvaporization of the spray is facilitated and also that the penetrationof the reagent into the substrate is improved.

According to one aspect of the invention, the mixture of fatty acidhalide and solvent comprises 0.1-20 wt %, preferably 0.1-10 wt %, morepreferably 0.1-5 wt % solvent of the total weight of the mixture. If thesolvent amount is too high, the reagent can be too diluted to form aneven coverage and distribution upon application, and thereby increasingthe need of increased application units. This can also result in ahigher risk of residual solvent molecules in the final product. If theapplied amount of reagent becomes too low, it can have a negative impacton the desirable material properties.

According to yet another aspect of the invention, the dry content of thecellulose substrate is above 80%, preferably above 85%, even morepreferably above 90%. The higher dry content, the better will the resultof the subsequent hydrophobation be. This is due to that the fatty acidhalide has a high reactivity towards water. Therefore, presence of watercan lead to the undesired formation of too high amounts of fatty acidsthat are not attached to the substrate.

According to yet another aspect of the invention, the fatty acid halideto be vaporized comprises an aliphatic chain length of between 10-22carbon atoms. Said fatty acid is preferably selected from palmitoylchloride (C16), stearoyl chloride (C18) or mixtures thereof.

According to yet another aspect of the invention, the method furthercomprises a step of heating the cellulose substrate, before and/or afteradding the fatty acid halide.

FIGURES

In the following, the invention will be described further with referenceto the drawings, wherein:

FIG. 1 shows a schematic view of the invention according to a firstembodiment, where a fatty acid halide in spray form is applied onto asubstrate;

FIG. 2 shows a schematic view of the invention according to a secondembodiment, where a fatty acid halide in vaporized form is applied ontoa substrate;

FIGS. 3a-b show schematic views of the invention according to a thirdand fourth embodiments, wherein both the first and second sides of asubstrate are subjected to a fatty acid halide;

FIG. 4 shows a schematic view of the invention according to a fifthembodiment, where a fatty acid halide in vaporized form is applied ontoa substrate; and

FIG. 5 illustrates in a schematic way hydrophobation of a cellulosesubstrates, where such substrates are in the form of three-dimensionalcellulose-based products.

DETAILED DESCRIPTION

The following detailed description illustrates examples of setups forperforming the method according to the invention, which may serve toillustrate the principles of the inventive idea in a non-limiting way.

In FIGS. 1-4, a cellulose substrate 1, comprising a first side and asecond side, is generally referred to as “1”. In these embodiments, thesubstrate is in the form of a cellulose-based web such as a paper- orpaperboard web. The second side of said substrate 1 faces away from thefirst side. The cellulose substrate, e.g. a paper- or paperboard web 1,is dried in a drying step. The drying is performed by any conventionaldrying methods suitable for drying a cellulose substrate. A cellulosesubstrate of a paper- or paperboard web may for example be dried bydrying cylinders. After the drying step, the cellulose substrate 1 has adry content above 80%, preferably above 85% and most preferably above90%. A higher dry content can give better results of the subsequenthydrophobation by obtaining a higher covalent degree.

The cellulose substrate 1 may thereafter be further dried and heated.The heating is preferably performed in a pre-treatment step by IRheating 2 as illustrated in FIGS. 1-3. The pre-treatment heating stephas several advantages. It will minimize unwanted condensation of thegas upon contact with the substrate, and also lead to that thesubsequent hydrophobizing agent will penetrate better through thesubstrate. Moreover, any remaining water residues can be further dried;the substrate 1 may possibly be dried even up to 95% dry content.

The first side of the dried and heated substrate 1 is then treated witha fatty acid halide, in spray form or in gas-phase, to hydrophobize thesubstrate, such that the substrate becomes hydrophobic. This isaccomplished by means of a device 5 (also referred to as “spray device”5) for dispersing liquid fatty acid halide into a spray 50, which spraymay contact the substrate directly or become vaporized into gas phasewhere such gas contacts the substrate. Said spray device 5 may be in theform of a spray nozzle used for atomizing the liquid. “Sprayatomization” here means the transformation of a liquid into a spray offine particles by mixing the liquid with compressed air. A spray nozzlegenerates the atomized spray when being passed through an opening athigh pressure and in a controlled manner. A higher pressure will createsmaller liquid droplets and a finer spray. Different spray devices 5 areconceivable.

Another example is electrospraying whereby electrical forces areutilized on a liquid that flows from a nozzle, which can have variousshapes and conformation, and thereafter fine, uniform and chargeddroplets are formed, due to that the electrical force exceeds thesurface tension force. It can also be due to mechanical distortions. Thegeneral advantages of the electrospraying process are that it can beperformed as one step at low cost, low energy input and with a goodflexibility. Ambient temperatures and pressures also work.

Upon that said first side of the dried and heated substrate 1 has beentreated with a fatty acid halide, the applied fatty acid halide will atleast partially penetrate the cellulose of said substrate 1 and bindcovalently to the cellulose therein, increasing the water repellency ofthe material. In order to enhance the penetration of the spray or gasthrough the substrate, the second side of the substrate can be subjectedto a vacuum suction, simultaneously, during the hydrophobation of thesubstrate, such that the spray or gas is transported in a predetermineddirection through the substrate. This enhances the hydrophobicity of thesurface as well as the core of the substrate, so that the substrate willbe more resistant against in-plane edge penetration.

The fatty acid halide is any halide that can be vaporized, howeverpalmitoyl chloride, C16 has, in tests, shown to be particularlysuitable. During tests a covalent degree of above 40% and even above 60%has been achieved, compared to conventional AKD sizing where no or justa small percentage of covalent binding can be obtained, which results inlow retention, which thereby leads to e.g. migration problems, stainsand machine stops etc.

Another advantage with use of spray combined with gas/vaporization forapplying the fatty acid halide is that it is very position specific andhydrophobicity is only achieved where the spray or gas can access thesubstrate. The reagent will react with the available hydroxyl groupsforming HCl as a by-product. The reagent is also highly reactive towardswater and the reaction requires dry substrates. Nevertheless, there willalways be some presence of water whereupon the corresponding, lessreactive, fatty acid also will be formed as an unbound molecule. It istherefore impossible to achieve 100% covalent degree. Yet, otheradvantages with the use of a gas-phase reaction is that the gas can bepenetrated and guided through the substrate more easily, the reactioncan be faster and a lower amount of chemical reagents may be neededcompared to application of the same reagent in a liquid state.

FIG. 1 illustrates an exemplary way of performing the method accordingto the invention. A dried and heated cellulose substrate 1 in the formof a paper- or paperboard is additionally heated and dried with IRheating from an IR heating box 2. The additional IR heating is optional.

Liquid fatty acid halide is stored in a separate tank 3 wherefrom it isejected through a device 5 for dispersing the liquid into a spray 50.Such spray device 5 can for instance be in the form of a spray nozzleused for atomizing the liquid, i.e. breaking up the fluid into droplets50. In the present example, the droplets are sprayed by means of thedevice 5 onto a first side 1 a of the underlying, running substrate 1.Said first side 1 aside of the substrate 1 is at the same time incontact with a downstream rotating cylinder 6, for instance a heatedcylinder that heats the droplets into gas whereby the atomized fattyacid molecules react more efficiently with the cellulose of thesubstrate. It is conceivable to arrange multiple spraying unitspositioned after each other in sequences in connection to the runningsubstrate, where each such unit can comprise one or a plurality ofspraying nozzles. This would enable for application of fatty acid inconsecutive steps, whereby smaller doses can be applied several timesinstead of one unit applying the whole amount at one occasion. Suchprocedure may in some cases improve the penetration of the reagent inthe thickness of the cellulose web.

It is also conceivable that a rotating vacuum cylinder with holes (notshown) is arranged in connection with a second side 1 b of the substrateand downstream of the spray device 5, arranged to vacuum suckingdroplets or vaporized fatty acid halide in a predetermined directionthrough the cellulose substrate 1. Thereby, the cellulose substrate 1can be hydrophobized through the complete thickness of the substrate.

Another arrangement for applying the fatty acid halide is that thesubstrate 1 is arranged to enter between two nip rolls (not shown),preferably where at least one of the rolls is a heated nip roll, andthat the fatty acid halide spray is directed into the nip roll junctionwhereby the spray droplets are converted into gaseous phase by means ofthe heated roll/s. In this arrangement, the spray may also be directedto contact the heated nip roll immediately upstream of the nip rolljunction, whereby the fatty acid halide is vaporised by the heat of theroll and directly thereafter, i.e. within seconds or milliseconds,applied onto the substrate.

Yet another arrangement for applying the fatty acid halide is that thefatty acid halide is sprayed directly onto a heating roll arranged toimmediately, i.e. within seconds or milliseconds, transfer said fattyacid halide onto a running substrate. Upon contacting the substrate, theheat from the roll will transform the fatty acid halide into gas phasemeaning that the vaporization occurs simultaneously with that the fattyacid halide is brought into contact with the substrate. In suchembodiment, the heated roll provides several functions: the function ofbringing the fatty acid halide into contact with the substrate, thefunction of vaporizing the fatty acid halide into gas phase and thefunction of promoting the chemical reaction to covalent bind the fattyacid halide to the substrate. Vaporization of the fatty acid halide canbe arranged to occur before the heated roll contacts the substrate, orsimultaneously with that the heated roll contacts the substratedepending on where on the heated roll the spray is applied. E.g. if thespray is directed so that the fatty acid halide hits the heated roll asmall distance prior to that said roll contacts the substrate thevaporization will take place before contact, whereas in case the sprayis directed so that the fatty acid halide hits the heated roll at thenip between the roll and the substrate the vaporization will take placesimultaneous to contact. If not all the spray is vaporized, it willstill be distributed in a uniform matter on the roll and then be takenup by the board in droplet form.

Moreover, the HCl by-product and possibly unreacted e.g. palmitoylchloride and/or unbound C16 can be removed and collected for handling.

In FIG. 2, a second embodiment according to the present invention isschematically shown. Herein, a dried and heated cellulose substrate 1 inthe form of a paper- or paperboard is optionally further heated anddried with IR heating from an IR heating box 2, as also previouslydescribed in connection with FIG. 1.

Liquid fatty acid halide is stored in a separate tank 3 wherefrom it istransferred e.g. via a tube 4 (or other transferring means) to a device5 for dispersing the liquid into a spray 50. Such device 5 can forinstance be in the form of a spray nozzle used for atomizing the liquid,i.e. breaking up the fluid into droplets 50. In the present example, thedroplets are sprayed via the device 5 into a heating chamber 7 such as apressurized heating tank 7. The spray droplets are heated inside saidtank 7 to vaporize into gas-phase, and said gas 70 is thereafter ejectedor deposited through a gas spreading device 71 onto the first surface ofsaid substrate 1. Said first side of the substrate is at the same timein contact with a rotating cylinder 6. Yet another rotating cylinder ofvacuum type may be arranged at the second side 1 b of the substrate forsucking the gas in a predetermined direction through the cellulosesubstrate 1. Thereby, the cellulose substrate 1 can be hydrophobizedthrough the complete thickness of the substrate. Any HCl by-product andpossibly unreacted e.g. palmitoyl chloride and/or unbound C16 can beremoved and collected for handling.

For both exemplified methods shown in FIGS. 1-2, it is possible tofirstly treat the first side of the substrate and subsequently treat thesecond side of the substrate with an additional unit facing the secondside of the substrate. Such treatment of both sides ensures that thewhole core of substrate will be modified. The usage of two or more sprayunits can be placed in such way that the minimum amount of space isneeded and fitted to the existing equipment. By utilizing a plurality ofunits, it can also be possible to run the machine at an increased speed.

FIGS. 3a-b show a third and fourth embodiment, respectively, whereinboth the first and second side of a substrate 1 are subjected tohydrophobation by means of application of a fatty acid halide in sprayform.

Referring to FIG. 3a , the substrate 1 is firstly subjected topre-treatment 2 in the form of heating, e.g. IR heating. A device 5 fordispersing liquid into spray is positioned downstream of thepre-treatment 2 at the second side 1 b of the substrate, adjacent to arotating cylinder 6 and arranged to direct a spray 50 of fatty acidhalide onto the surface of the cylinder 6 which, upon rotating further,will deliver the fatty acid halide onto the surface of the second side 1b of the substrate 1. The rotating cylinder 6 may be heated, also tosuch extent that the sprayed droplet transform into gas before touchingthe substrate. A vacuum box 8 is arranged at the first side 1 a of thesubstrate 1 to draw the reagent into the cellulose structure. Accordingto the herein described third embodiment, the substrate 1 is furtherhydrophobized in a subsequent downstream step, wherein fatty acid halide50′ is applied also onto the first side 1 a of the substrate 1.Accordingly, as seen in FIG. 3a , a second device 5′ for dispersingliquid into spray 50′ is positioned adjacent to a second rotatingcylinder 6′, said device 5′ being arranged to direct a spray 50′ offatty acid halide onto the surface of the cylinder 6′ which, uponrotating further, will deliver the fatty acid halide onto the surface ofthe first side 1 a of the substrate 1. The rotating cylinder 6′ may beheated. A vacuum box 8′ is arranged in close proximity of the rotatingcylinder, at the second side 1 b of the substrate, to guide the reagentto at least partially penetrate the substrate 1. The skilled personunderstands that the equipment (e.g. spray device 5, 5′; vacuum box 8,8′; cylinder 6, 6′ etc) are interchangeable and that it is possible tofirstly treat the first side 1 a of the substrate 1 and thereafter thesecond side 1 b.

A fourth embodiment according to the invention is seen in FIG. 3b ,serving the same purpose as in FIG. 3a , namely to treat both sides of asubstrate 1 to increase the hydrophobicity thereof. In a similar manneras described for FIG. 3a , the substrate 1 is guided through twosubsequent hydrophobation steps wherein fatty acid halide is appliedfirstly onto the second side 1 b of the substrate, and secondly onto thefirst side 1 a thereof. In the first step, a spray device 5 ispositioned adjacent to a second side 1 b of the running substrate 1 andis arranged to direct a spray 50 of fatty acid halide directly onto saidsurface 1 b. A vacuum box 8 is arranged at the first side 1 a of thesubstrate, opposing the spray device 5, said vacuum box 8 being arrangedto draw the fatty acid halide to at least partially penetrate thesubstrate by means of vacuum suction. A downstream rotating cylinder 6may be provided, preferably a heated cylinder, to promote the binding ofreagent to the cellulose substrate 1. A corresponding, secondhydrophobation step is arranged downstream of the first cylinder 6,whereby fatty acid halide is applied also onto the first side 1 a of thesubstrate in a corresponding manner as described for the firsthydrophobation step.

The fatty acid halide in the fourth embodiment can be converted fromspray form to gaseous form before being guided to contact the substrate1.

In FIG. 4, a fifth embodiment according to the present invention isshown. Herein, heating of the substrate 1 is performed in apre-treatment step e.g. by IR heating 2. The subsequently appliedvaporized fatty acid halide 70 is guided to contact the substrate 1 byvacuum sucking 8 at the first side 1 a of the cellulose substrate, sothat the vaporized fatty acid 70 is brought to be transferred along thesurface of the first side 1 a of the cellulose substrate 1 in apredetermined direction and contact the first surface 1 a. The vaporizedfatty acid is thereby brought to move substantially parallel with thefirst side of the substrate.

FIG. 5 illustrates in a schematic way the method according to theinvention where the substrate 10 is a three-dimensional cellulose basedproduct. Herein, a conveyor belt 9 is transferring a plurality ofthree-dimensional cellulose products 10 through a unit 11 arranged tohydrophobize said products by means of the method of claim 1. Said threedimensional products 11 may be e.g. pre-produced paper trays, mugs orcontainers, or other types of 3D-shaped objects made from cellulose.After having passed through the unit 11 wherein vaporized fatty acidhalide is brought to contact the cellulose substrate, and at leastpartially penetrated its thickness, the exiting product 10′ has acquiredhydrophobic properties.

To characterize the success of the reaction, contact angle measurementwas utilized to qualitatively analyze how much the cellulose substratehas been hydrophobized by the method. An un-treated cellulose substratehad before a contact angle around 40° and after treatment of theinventive method a contact angle of 110-130° on both the first side andthe second side of the substrate, despite only one surface was in directcontact with the reagent. Contact angles greater than 90° (high contactangle) generally means that wetting of the surface is unfavourable, sothe fluid will minimize contact with the surface and form a compactliquid droplet.

In view of the above detailed description of the present invention,other modifications and variations will become apparent to those skilledin the art. For example, the method according to the invention may beused as a complement to other methods of application of fatty acidhalide onto a substrate. However, it should be apparent that such othermodifications and variations may be affected without departing from thespirit and scope of the invention.

1. A method for hydrophobizing a cellulose substrate, which comprises afirst side and a second side facing away from the first side, whereinthe method comprises the steps of: drying the cellulose substrate to adry content above 80%; providing a fatty acid halide in spray form;converting said fatty acid halide in spray form into vaporized fattyacid halide; and guiding said vaporized fatty acid halide to contact thefirst side of the cellulose substrate, and at least partially penetratethe cellulose substrate.
 2. The method according to claim 1, furthercomprising the step of: guiding said fatty acid halide to contact thesecond side of the cellulose substrate, and at least partially penetratethe cellulose substrate.
 3. The method according to claim 1, whereinsaid guiding of the fatty acid halide is performed by vacuum sucking atthe second side of the cellulose substrate, such that the vaporizedfatty acid penetrates the cellulose substrate in a predetermineddirection through the cellulose substrate.
 4. The method according toclaim 1, wherein said guiding of the vaporized fatty acid halide isperformed by vacuum sucking at the first side of the cellulosesubstrate, such that the vaporized fatty acid is guided along a surfaceof the first side of the cellulose substrate in a predetermineddirection whereby the fatty acid is brought into contact with thecellulose substrate.
 5. The method according to claim 1, wherein the drycontent of the cellulose substrate is above 90%.
 6. The method accordingto claim 1, wherein the fatty acid comprises an aliphatic chain lengthof between 10-22 carbon atoms.
 7. The method according to claim 1,wherein the fatty acid comprises palmitoyl chloride, C16, stearoylchloride, C18, or mixtures thereof.
 8. The method according to claim 1,wherein the fatty acid to be sprayed is mixed with at least one solventor a mixture of solvents, wherein the at least one solvent or a mixtureof solvents is preferably selected from a group consisting of: acetone,ethyl acetate, and methyl ethyl ketone.
 9. The method according to claim8, wherein the mixture of fatty acid halide and the at least one solventor a mixture of solvents comprises 0.1-20 wt %.
 10. The method accordingto claim 1, wherein the cellulose substrate is a paper- or paperboardweb.
 11. The method according to claim 10, wherein the web is a single-or multilayer web.
 12. The method according to claim 1, wherein thecellulose substrate comprises a three-dimensional cellulose-basedproduct.
 13. The method according to claim 1, further comprising a stepof: heating the substrate, before, or after, or before and after addingthe fatty acid halide.
 14. The method according to claim 13, wherein theheating step is performed by IR heating.
 15. The method according toclaim 3, wherein the vacuum sucking is performed by a vacuum box. 16.The method according to claim 1, wherein the vacuum sucking is performedby a rotating vacuum cylinder.
 17. The method according to claim 1,wherein the step of converting said spray form fatty acid halide intovaporized fatty acid halide is performed by IR heating.
 18. A cellulosebased product having been treated by the method according to claim 1.19. The method according to claim 1, wherein the dry content of thecellulose substrate is above 85%.
 20. The method according to claim 8,wherein the mixture of fatty acid halide and the at least one solvent ora mixture of solvents comprises 0.1-10 wt % solvent.